Recirculation of engine exhaust is believed to reduce oxides of nitrogen in combustion products that are emitted to atmosphere from an internal combustion engine. A known EGR system employs an EGR valve that is controlled in accordance with engine operating conditions. Under certain operating conditions, the known EGR valve prevents exhaust gases from flowing into the intake manifold, and during other operating conditions, the EGR valve permits a controlled amount of exhaust gases into the intake manifold. Thus, the known EGR valve regulates the amount of engine exhaust gas that is delivered to an intake system and mixed with a fuel-air mixture that is to be combusted in the engine. It is believed that mixing exhaust gas with the fuel-air mixture limits combustion temperatures and hence reduces the formation of oxides of nitrogen.
The promulgation by various governmental agencies of stringent exhaust emissions regulations has created a need for improved control of EGR valves. Electric actuators are believed to provide one approach to improving EGR valve control; however, such actuators must also be able to operate properly over an extended period of usage in extreme environments that include wide temperature extremes and vibration. For example, it is known to mount an EGR valve to a manifold or a housing that has one port exposed to exhaust gases and another port exposed to an intake manifold of the engine.
Thus, it would be advantageous to provide an EGR system with a valve that improves control of tailpipe emissions, improves vehicle drivability, and/or improves vehicle fuel economy.